The present invention relates to a method for qualifying a local loop for digital subscriber line (DSL) service.
xDSL is a generic term for digital subscriber line equipment and services, including packet-based architectures, such as ADSL, HDSL, SDSL, IDSL VDSL, and RADSL. DSL technologies provide extremely high bandwidth over embedded twisted pair, copper cable plant. DSL technologies offer great potential for bandwidth-intensive applications.
ADSL or asymmetric digital subscriber line services generally use existing unshielded twisted pair (UTP) copper wires from the telephone company""s central office to the subscriber""s premise. ADSL modems at both the central office and the subscriber""s premise send high-speed digital signals up and down the copper wires. The ADSL flavor of DSL services is capable of providing a downstream bandwidth of about 1.5 Mbps-6.144 Mbps, and an upstream bandwidth of about 32 Kbps-640 Kbps with loop distances ranging from about 3.7 km-5.5 km.
HDSL or high bit rate digital subscriber line services provide a symmetric, high-performance connection over a shorter loop, and typically require two or three copper twisted pairs. HDSL is capable of providing both upstream and downstream bandwidth of about 1.5 Mbps, over loop distances of up to about 3.7 km. SDSL or single line digital subscriber line services provide a symmetric connection that matches HDSL performance using a single twisted pair, but operating over a shorter loop of up to about 3.0 km. VDSL or very high bit rate digital subscriber line services are typically implemented in asymmetric form, as a very high speed variation on the ADSL theme over a very short loop. Specifically, target downstream performance is typically about 52 Mbps over UTP local loops of 300 m, 26 Mbps at 1,000 m, and 13 Mbps at 1,500 m. Upstream data rates in asymmetric implementations tend to range from about 1.6 Mbps to about 2.3 Mbps. Additionally, there is RADSL or rate adaptive asymmetric digital subscriber line services. RADSL provides a dynamic connection that adapts to the length and quality of the line.
In the DSL family of services, many DSL themes, including ADSL, HDSL, SDSL, IDSL, VDSL, and RADSL, utilize a packet-based approach that does away with the line-grabbing practice of circuit switched networks, such as ISDN (although ISDN service is a form of digital subscriber line). This packet-based approach is very advantageous in a variety of situations. IDSL provides a bandwidth of 128 Kbps and terminates on the customer side at an ISDN terminal adapter.
Of course, DSL services, also commonly referred to as simply DSL or digital subscriber line services, are much more dependent on line conditions than traditional telephone services. Traditional telephone services typically use a bandwidth including frequencies up to about 4 kilohertz, while the DSL services utilize a bandwidth including frequencies sometimes over 1 MHz. While some local loops are in great condition for implementing DSL services, that is, the local loops have short to moderate lengths with minimal bridged taps and splices, many local loops are not as clean. For example, local loop length varies widely, for example, from as short as a few hundred meters to as long as several kilometers.
Further, the wire gauge for a local loop is almost always not continuous over the length of the loop. That is, a portion of the local loop may be one wire gauge, while an adjacent portion of the local loop has a different wire gauge, with the two portions being spliced together. Still further, many existing local loops have one or more bridged taps. A bridged tap is a length of wire pair that is connected to a loop at one end and is unterminated at the other end. Sometimes, an existing local loop will have several bridged taps so that the telephone company may connect a customer to any one of the taps (while leaving the other taps unterminated). Tapped lines may allow the telephone company to better utilize its copper cable plant distribution. For example, a particular service area may include 25 residences. Because not all residences require multiple phone lines, there may be a total of about 30 or 35 local loops, with some of the loops having multiple bridged taps. As such, it may be possible for any one of the residences to order multiple line service, so long as only a few of the residences do so.
Because so many different factors affect the success of a DSL solution, the question of whether or not a particular local loop qualifies for any level of DSL service is a complicated one. Due to varying line conditions, some loops may qualify for the highest quality DSL service, while other loops only qualify for a very limited bandwidth, and still, some of the loops do not qualify at all for DSL service. The steps involved in determining the quality of DSL service that is available on a particular loop is called the loop qualification process. In an existing loop qualification process, a customer calls a DSL service provider and inquires as to the availability of DSL service. The customer service representative then performs a database look-up on the customer""s line and evaluates the ability to receive DSL service. The database record indicates line quality on an aggregate basis. That is, a record may generally indicate the conditions of all lines in a medium sized group of lines. If the customer service representative believes that further inquiry is required, he/she may test the circuit with voice band measurement devices.
Unfortunately, the accuracy of some database records is questionable and it has been found that line quality may vary widely even among lines in the same medium sized group. Further, voice band measurements do not always accurately reflect the ability of a loop to support DSL services. As such, many times the customer cannot know the actual available bandwidth for DSL services until after customer premise equipment has been purchased and installed at the customer residence. If, after several steps have been taken to implement a DSL solution, it is then determined that the local loop is in such poor condition that DSL cannot be supported or that the local loop does not support as much bandwidth as the customer anticipated, there can be a lot of disappointment for both the customer and the service provider.
For the foregoing reasons, there is a need for a method that allows a customer to determine whether or not a local loop is capable of receiving DSL service that overcomes the limitations associated with the prior art.
It is, therefore, an object of the present invention to provide a loop qualification tool and method for DSL service that qualifies the loop on an individual basis and, as appropriate, uses data from multiple sources.
In carrying out the above object, a method for qualifying a local loop for a digital subscriber line service is provided. The loop has a provider end and a customer end. The method comprises determining a provider end to customer end path for the local loop. The end to end path identifies the loop on an individual basis with respect to a plurality of other loops. The method further comprises determining a set of loop description data, identifying a state of the set of loop description data, and determining a qualification result for the local loop. The set of loop description data corresponds to the end to end path of the local loop. The qualification result is based on the set of loop description data and is further based on a different data source as dictated by the state of the set of loop description data. That is, the loop is qualified on an individual basis, and as appropriate multiple information sources are checked to qualify the loop.
Embodiments of the present invention may be suitable for a number of different digital subscriber line (DSL) applications. The inventors believe that embodiments of the present invention are suitable for carrierless amplitude phase (CAP) line encoding and rate adaptative asymmetric digital subscriber line (RADSL) applications. Of course, embodiments of the present invention may be suitable for other applications, such as discrete multi-tone (DMT) line encoding DSL applications. Further, it is appreciated that embodiments of the present invention may be suitable for many DSL solutions including, for example, ADSL, HDSL, SDSL, IDSL, ISDN, VDSL, and RADSL, and solutions utilizing various portions of the frequency spectrum in various ways.
In one embodiment, determining the provider end to customer end path further comprises accessing a loop facilities assignment system. The system has records indicating the end to end paths for the loops. In one embodiment, determining the set of loop description data further comprises accessing a physical description database having records indicating the loop description data. The loop description data for a loop may include lots of different information. For example, wire gauge information, bridged tap information, segment information and load coil information are all examples of information that may be included in the loop description data, on an individual loop basis. Further, the loop description data may include an identifier indicating a state from a plurality of states including an actual state and a planned state for the data. As such, in some embodiments, the qualification result is further based on the different data source when the identifier indicates a planned state. Actual data should not require multiple data sources.
The different data source may be, for example, loop test data corresponding to the end to end path of the local loop. The test data could be based on capacitance measurements, such as mechanized loop testing (MLT) data. In another example, the different data source may include a set of characteristic data corresponding to a group of loops including the local loop. The characteristic data allows estimates to be made for the particular local loop being analyzed. For example, weighted averages could be used to estimate a description for the loop. Further, in another example, a geographic system may supply data. The geographic system could be a geographical information system (GIS) that uses a follow the road routine to estimate distances.
Further, in carrying out the present invention, a method for qualifying a local loop for a digital subscriber line service is provided. The loop has a provider end and a customer end. The method comprises determining a provider end to customer end path. The end to end path identifies the loop on an individual basis with respect to a plurality of other loops. The method further comprises determining a set of loop description data, identifying a state of the set of loop description data, and estimating an insertion loss. The loop description data corresponds to the end to end path of the local loop. The insertion loss is based on the set of loop description data and is further based on a different data source as dictated by the state of the set of loop description data. That is, loop description data is for the individual loop, not an aggregate. Further, multiple information sources are used, as required.
In some embodiments, the method further comprises determining a qualification result based on the insertion loss. In a suitable implementation, the insertion loss is estimated in accordance with carrierless amplitude phase (CAP) line encoding. In some embodiments, the method further comprises selecting an average frequency for CAP line encoding, and estimating the insertion loss for the local loop at the average frequency. The average frequency may be, for example, about 196 kHz kilohertz. In some embodiments, the method further comprises estimating an available bandwidth based on the insertion loss.
The advantages associated with embodiments of the present invention are numerous. For example, embodiments of the present invention operate to perform real-time analysis of customer loops that generates responses indicating if the loop qualifies or not, and if it does qualify, at what estimated maximum bandwidth. Embodiments of the present invention have solved the problem of analysis of loops at the individual loop level, as opposed to the higher, aggregate level approach that is used by the prior art. In a preferred implementation, an embodiment of the present invention provides a web based interfaced to qualify customer loops based on analysis of stored loop data acquired from various data sources.
The above object and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.